Add more hip_bug.md entry, regarding hang after hipLaunchKernel

Change-Id: I5800cb627179ec0e913cd36d332fb8c2994ab71e

docs/markdown/hip_bugs.md

@@ -2,7 +2,8 @@
 
 <!-- toc -->
 
-- [Errors related to undefined reference to `__hcLaunchKernel__***__grid_launch_parm**](#error-undefined-reference)
+- [Errors related to undefined reference to `__hcLaunchKernel__***__grid_launch_parm**](#errors-related-to-undefined-reference-to-hclaunchkernel__grid_launch_parm)
+- [Application hangs after a hipLaunchKernel call](#what-if-i-see-application-hangs-after-a-hiplaunchkernel-call)
 
 <!-- tocstop -->
 
@@ -22,3 +23,11 @@ namespace {
 __global__ MyKernel …
 - Avoid calling member functions 
 
+
+### What if I see application hangs after a hipLaunchKernel call?
+If hipLaunchKernel takes parameters that request explicitly memcpy, then it will cause application hang. 
+Reason is that the hipLaunchKernel macro locks the stream.  
+If kernel paramters are actually function calls which invoke other hip apis (i.e. memcpy) to the same stream, then deadlock occurs.
+
+To workaround, try:
+Move the function calls so they occur outside the hipLaunchKernel macro, store results in temps, then use the tems inside the kernel.